Exendin-4 is a 39 amino acid peptide which is produced by the salivary glands of the Gila monster (Heloderma suspectum) (Eng, J. et al., J. Biol. Chem., 267:7402-05, 1992). Exendin-4 is an activator of the glucagon-like peptide-1 (GLP-1) receptor, whereas it does not activate significantly the glucagon receptor.
Exendin-4 shares many of the glucoregulatory actions observed with GLP-1. Clinical and nonclinical studies have shown that exendin-4 has several beneficial antidiabetic properties including a glucose dependent enhancement in insulin synthesis and secretion, glucose dependent suppression of glucagon secretion, slowing down gastric emptying, reduction of food intake and body weight, and an increase in beta-cell mass and markers of beta cell function (Gentilella R et al., Diabetes Obes Metab., 11:544-56, 2009; Norris S L et al, Diabet Med., 26:837-46, 2009; Bunck M C et al, Diabetes Care., 34:2041-7, 2011).
These effects are beneficial not only for diabetics but also for patients suffering from obesity. Patients with obesity have a higher risk of getting diabetes, hypertension, hyperlipidemia, cardiovascular and musculoskeletal diseases.
Relative to GLP-1, exendin-4 is resistant to cleavage by dipeptidyl peptidase-4 (DPP4) resulting in a longer half-life and duration of action in vivo (Eng J., Diabetes, 45 (Suppl 2):152A (abstract 554), 1996).
Exendin-4 was also shown to be much more stable towards degradation by neutral endopeptidase (NEP), when compared to GLP-1, glucagon or oxyntomodulin (Endocrinology, 150(4), 1712-1721, 2009). Nevertheless, exendin-4 is chemically labile due to methionine oxdiation in position 14 (Hargrove D M et al., Regul. Pept., 141: 113-9, 2007) as well as deamidation and isomerization of asparagine in position 28 (WO 2004/035623).
The amino acid sequence of exendin-4 is shown as SEQ ID NO: 1
HGEGTFTSDLSKQMEEEAVRLFIEWLKNGGPSSGAPPPS-NH2
The amino acid sequence of GLP-1(7-36)-amide is shown as SEQ ID NO 2
HAEGTFTSDVSSYLEGQAAKEFIAWLVKGR-NH2
Liraglutide is a marketed chemically modified GLP-1 analog in which, among other modifications, a fatty acid is linked to a lysine in position 20 leading to a prolonged duration of action (Drucker D J et al, Nature Drug Disc. Rev. 9, 267-268, 2010; Buse, J. B. et al., Lancet, 374:39-47, 2009).
The amino acid sequence of Liraglutide is shown as SEQ ID NO 4.
HAEGTFTSDVSSYLEGQAAK((S)-4-Carboxy-4-hexa- decanoylamino-butyryl-)EFIAWLVRGRG-OH
Glucagon is a 29-amino acid peptide which is released into the bloodstream when circulating glucose is low. Glucagon's amino acid sequence is shown in SEQ ID NO 3.
HSQGTFTSDYSKYLDSRRAQDFVQWLMNT-OH
During hypoglycemia, when blood glucose levels drop below normal, glucagon signals the liver to break down glycogen and release glucose, causing an increase of blood glucose levels to reach a normal level. Hypoglycemia is a common side effect of insulin treated patients with hyperglycemia (elevated blood glucose levels) due to diabetes. Thus, glucagon's most predominant role in glucose regulation is to counteract insulin action and maintain blood glucose levels.
Hoist (Hoist, J. J. Physiol. Rev. 2007, 87, 1409) and Meier (Meier, J. J. Nat. Rev. Endocrinol. 2012, 8, 728) describe that GLP-1 receptor agonists, such as GLP-1, liraglutide and exendin-4, have 3 major pharmacological activities to improve glycemic control in patients with T2DM by reducing fasting and postprandial glucose (FPG and PPG): (i) increased glucose-dependent insulin secretion (improved first- and second-phase), (ii) glucagon suppressing activity under hyperglycemic conditions, (iii) delay of gastric emptying rate resulting in retarded absorption of meal-derived glucose.
Pocai et al (Obesity. 2012; 20:1566-1571; Diabetes 2009, 58, 2258) and Day et al. (Nat Chem Biol 2009; 5:749) describe that dual activation of the GLP-1 and glucagon receptors, e.g., by combining the actions of GLP-1 and glucagon in one molecule leads to a therapeutic principle with anti-diabetic action and a pronounced weight lowering effect
Peptides which bind and activate both the glucagon and the GLP-1 receptor (Hjort et al. Journal of Biological Chemistry, 269, 30121-30124, 1994; Day J W et al, Nature Chem Biol, 5: 749-757, 2009) and suppress body weight gain and reduce food intake are described in patent applications WO 2008/071972, WO 2008/101017, WO 2009/155258, WO 2010/096052, WO 2010/096142, WO 2011/075393, WO 2008/152403, WO 2010/070251, WO 2010/070252, WO 2010/070253, WO 2010/070255, WO 2011/160630, WO 2011/006497, WO 2011/152181, WO 2011/152182, WO2011/117415, WO2011/117416, and WO 2006/134340, the contents of which are herein incorporated by reference.
In addition, triple co-agonist peptides which not only activate the GLP-1 and the glucagon receptor, but also the GIP receptor are described in WO 2012/088116 and by VA Gault et al (Biochem Pharmacol, 85, 16655-16662, 2013; Diabetologia, 56, 1417-1424, 2013).
Bloom et al. (WO 2006/134340) disclose that peptides which bind and activate both the glucagon and the GLP-1 receptor can be constructed as hybrid molecules from glucagon and exendin-4, where the N-terminal part (e.g. residues 1-14 or 1-24) originate from glucagon and the C-terminal part (e.g. residues 15-39 or 25-39) originate from exendin-4.
D E Otzen et al (Biochemistry, 45, 14503-14512, 2006) disclose that N- and C-terminal hydrophobic patches are involved in fibrillation of glucagon, due to the hydrophobicity and/or high β-sheet propensity of the underlying residues.
Compounds of this invention are exendin-4 peptide analogues comprising leucine in position 10 as well as position 13.
Krstenansky et al (Biochemistry, 25, 3833-3839, 1986) show the importance of the residues 10-13 of glucagon (YSKY) for its receptor interactions and activation of adenylate cyclase. In the exendin-4 derivatives described in this invention, several of the underlying residues are different from glucagon. In particular residues Tyr10 and Tyr13, which are known to contribute to the fibrillation of glucagon (D E Otzen, Biochemistry, 45, 14503-14512, 2006) are replaced by Leu, a non-aromatic amino acid, in position 10 as well as position 13. This replacement, especially in combination with isoleucine in position 23 and glutamate in position 24, leads to exendin-4 derivatives with potentially improved biophysical properties as solubility or aggregation behaviour in solution. In addition, this replacement together with Leu in position 14 leads to the formation of a so called LXXLL motif. It is known from the literature that such LXXLL motifs have a high predisposition to form a α-helical structure upon binding (Ji-Hye Yun et al., Bull. Korean Chem. Soc. 2012, Vol. 33, No. 2 583, A: K. Shiau et al. Cell, 1998, 95, 927-937.) Surprisingly it was found that the compounds of this invention show a high activity on the glucagon receptor.
Compounds of this invention are more resistant to cleavage by neutral endopeptidase (NEP) and dipeptidyl peptidase-4 (DPP4), resulting in a longer half-life and duration of action in vivo, when compared with GLP-1 and glucagon. Compounds of this invention preferably are soluble not only at neutral pH, but also at pH 4.5. This property potentially allows co-formulation for a combination therapy with an insulin or insulin derivative and preferably with a basal insulin like insulin glargine/Lantus®.